Actuator arrangement and fuel injector incorporating an actuator arrangement

ABSTRACT

An actuator arrangement for use in a fuel injector of an internal combustion engine, including an inner core ( 40 ) comprising a collar ( 48 ) and a core region ( 44 ) having a plurality of laminates ( 140 ) stacked in the direction of a first lamination axis (L A ) and a first outer pole ( 42 ) for receiving at least a part of the core region ( 44 ). An electromagnetic winding ( 52 ) is received within a first volume defined between the first outer pole ( 42 ) and the core region ( 44 ). The collar ( 48 ) is formed from at least two collar parts ( 48   a   , 48   b ) which are adjustable relative to one another to alter the separation between them so as to accommodate core regions ( 44 ) of different diameter. The collar ( 48 ) is formed from a plurality of laminates ( 1, 2, 3, 4, 5 ) having a second lamination axis (A) which is perpendicular to the first lamination axis (L A ).

TECHNICAL FIELD

The present invention relates to an electromagnetic actuator arrangement. In particular, but not exclusively, the invention relates to an electromagnetic actuator arrangement for use in a fuel injector of an internal combustion engine. The invention also relates to a fuel injector incorporating an electromagnetic actuator arrangement.

BACKGROUND TO THE INVENTION

Referring to FIG. 1, it is known, for example from European Patent No EP 0987431 (Delphi Technologies Inc.), to provide a fuel injector 10 with two independently operable valve arrangements for controlling fluid pressure within the injector. The valve arrangements 12, 14 are arranged to control movement of a fuel injector valve needle 16 relative to a valve needle seating so as to control the delivery of fuel from the injector. Movement of the valve needle 16 away from the seating permits fuel to flow from an injector delivery chamber 17 through one or more outlet openings 18 of the injector into the engine or other combustion space. The injector delivery chamber 17 communicates with an injector supply passage 20 which, in turn, receives fuel from a high pressure pump chamber 23 forming part of the injector.

A first one of the valve arrangements is known as the control valve arrangement 12, or the nozzle control valve, and includes a control valve member which is movable between a first (open) position in which a communication path exists between an injector control chamber 22 at the back of the valve needle and a low pressure drain, and a second (closed) position in which the communication path is closed. The nozzle control valve is biased into the closed position by means of a spring. A second one of the valve arrangements takes the form of a spill or drain valve arrangement 14 which serves to control whether the pump chamber 23, and hence the fuel supply passage 20, communicates with the low pressure drain, or whether the communication path between the fuel supply passage 20 and the low pressure drain is closed. When the spill valve 14 is in a first (open) position the fuel supply passage 20 communicates with the low pressure drain and when the spill valve 14 is in the second (closed) position communication between the fuel supply passage 20 and the low pressure drain is closed. The spill valve is biased into the open position by means of the spring, which is shared with the nozzle control valve.

A surface associated with the valve needle 16 is exposed to fuel pressure within the control chamber 22 such that the pressure of fuel within the control chamber 22 applies a force to the valve needle 16 to urge the valve needle towards its seating, thereby closing the outlet openings 18. In this position, injection of fuel into the engine or other combustion space does not occur.

In order to commence injection, the nozzle control valve 12 is actuated such that the control valve member is moved into its open position, bringing the control chamber 22 into communication with a low pressure drain and causing fuel pressure within the control chamber 22 to be reduced. The force urging the valve needle 16 towards its seating is therefore reduced and, consequently, the valve needle 16 is caused to lift the valve needle 16 away from its seating due to the force of fuel pressure in the injector delivery chamber 17 to permit fuel to flow through the injector outlet openings 18.

In order to terminate injection, the nozzle control valve 12 may be de-actuated such that the control valve member is moved into its closed position, closing the connection between the control chamber 22 and the low pressure drain. The force acting on the valve needle 16 due to fuel pressure within the control chamber 22 is therefore increased, causing the valve needle 16 to be urged against its seating to terminate injection.

The nozzle control valve 12 thus operates to control the pressure differential between the fuel in the control chamber 22 and the fuel in the injector delivery chamber 17, that is to say the differential in the pressure acting to close the needle and the pressure serving to open it. In addition to the pressure of fuel in the control chamber 22 tending to urge the valve needle to close, a closing spring 21 is provided to assist the aforementioned closing force.

Another method of terminating injection is to use the spill valve arrangement 14. If the spill valve 14 is in the open position, fuel pressure within the fuel supply passage 20 (and hence the injector delivery chamber 17) is reduced so that the closing spring 21 urges the valve needle 16 against its seating, closing the outlet openings 18 in the injector body and terminating injection. If the spill valve 14 is in the closed position high pressure is re-established within the fuel supply passage 20 and the valve needle 16 is caused to lift against the spring force.

An actuator arrangement is provided to control both the nozzle control valve and the spill valve. The actuator includes first and second windings 24, 26 to which a current is supplied to control movement of first and second armatures, 28, 30 respectively. The first armature 28 is coupled to the nozzle control valve 12 so that energisation of the first winding 24 causes the first armature 28, and hence the nozzle control valve 12, to move between its closed and open positions. Energisation of the actuator causes the nozzle control valve 12 to move into the open position, whilst de-energisation of the actuator causes the nozzle control valve 12 to move into the closed position under the influence of the spring.

The second armature 30 is coupled to the spill valve 14 so that energisation of the second winding 26 causes the second armature 30, and hence the spill valve 14, to move between its open and closed positions. Energisation of the actuator causes the spill valve 14 to move into the closed position, whilst de-energisation of the actuator causes the spill valve 14 to move into the open position under the influence of the spring.

In other injector designs, the nozzle control valve 12 is not present so that only a spill valve 14 is provided. It is known in such arrangements to provide an electromagnetic actuator having a single winding to control operation of the spill valve.

In the injector shown in FIG. 1, each of the valves 12, 14 are controlled by means of a double pole actuator (i.e. the actuator arrangement takes the form of a twin, double pole actuator arrangement). In another known injector, such as that described in EP 1120563 A (Delphi Technologies, Inc.), two valves 12, 14 are provided but the nozzle control valve is controlled by means of a single pole actuator. The actuator part of an injector of this type is shown in FIG. 2. As in EP 0987431, the spill valve 14 is controlled by means of a double pole actuator. Like parts to those shown in FIG. 1 are identified with like reference numerals in FIG. 2.

It is desirable to reduce the eddy current effects that exist in the actuator cores of the injectors of the aforementioned type. There is also a requirement to improve the flux density capability. One way to achieve this is to provide the actuator with an inner core which is formed from a plurality of laminates, with a unitary outer pole of annular form receiving a part of the inner core. The winding of the actuator is received within the volume defined between the outer pole and the inner core. The combination of these features provides benefits for the magnetic performance of the actuator and also structural rigidity.

As the inner core is formed from a plurality of laminates, any deviation in the nominal thickness of the laminate sheet from which the layers are stamped will be compounded in the final core structure, resulting in a degree of ellipticity. This gives rise to manufacture and assembly problems, as not all nominally identical parts then fit conveniently with other parts of the actuator and/or actuator tooling parts. In particular, the winding bobbin by which the winding is wound onto the inner core requires a circular diameter inner core. It is an object of the present invention to address this problem.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided an actuator arrangement for use in a fuel injector of an internal combustion engine, the actuator arrangement including an inner core comprising a collar and a core region having a plurality of laminates stacked in the direction of (i.e. stacked along) a first lamination axis. A first outer pole receives at least a part of the core region, and an electromagnetic winding is received within a volume defined between the outer pole and the core region. The collar is formed from at least two collar parts which are adjustable relative to one another to alter the separation between them, thereby to accommodate core regions of different diameter.

Preferably, therefore, at least one of the laminates of the core region will be different in outer profile to its neighbouring laminate or laminates.

In a preferred embodiment, the collar is also formed from a plurality of laminates stacked in the direction of a second lamination axis which is perpendicular to the first lamination axis. Preferably, the first lamination axis is perpendicular to the actuator axis.

Lamination of the inner core of the actuator provides benefits for the magnetic performance of the actuator. It is particularly advantageous to laminate the core region of the actuator as this part is of reduced diameter, so the cross section viewed in the direction of eddy currents is relatively large. Thus, the invention enables eddy current effects to be reduced. Furthermore, as the collar is comprised of two parts which are movable relative to one another, it is readily compatible with core regions having different diameters. The diameter of the core region can vary if the thickness of its laminates differs from the nominal thickness, because in such circumstances it is necessary to adjust the layer profile to ensure the outer profile of the core region always has a circular outer periphery.

According to a second aspect of the invention, an actuator arrangement for use in a fuel injector of an internal combustion engine includes an inner core comprising a collar and a core region having a plurality of laminates stacked in the direction of a first lamination axis. A first outer pole receives at least a part of the core region, and an electromagnetic winding is received within a first volume defined between the first outer pole and the core region. The collar is formed from a plurality of laminates stacked in the direction of (i.e. stacked along) a second lamination axis which is perpendicular to the first lamination axis. In this aspect of the invention, the adjustability of the collar is only a preferred and/or optional feature.

In a preferred embodiment, the inner core comprises an upper core region (i.e. the afore-mentioned core region is an upper core region) which defines, together with the outer pole, the winding volume. In an injector application, the upper core region thus defines a pole of a double pole actuator for the spill valve of the injector.

Whereas lamination of the inner core of the actuator provides benefits for the magnetic performance of the actuator, the use of a unitary outer pole (for the upper core region in particular) provides structural rigidity. A combination of the two features is therefore particularly advantageous.

In a preferred embodiment, the plurality of laminates of the collar define an internal periphery which mates with an outer periphery defined by the laminates of the core region.

In a further preferred embodiment, the internal periphery of the collar and the plurality of laminates of the core region include a means for interlocking the outer collar and the core region together to ensure robustness of the inner core.

The means for interlocking may include a channel defined by the plurality of laminates of the core region and a projection provided on one or more of the plurality of laminates of the collar, wherein the projection is received within the channel. The inverse arrangement is also possible, wherein one or more of the plurality of laminates of the collar define a channel and one or more of the laminates of the core region is provided with a projection for receipt within the channel.

In one embodiment, the inner core comprises an upper core region which defines, together with the first outer pole, the first winding volume for the first electromagnetic winding.

Preferably, the inner core further comprises a lower core region which defines, at least in part, a second volume for receiving a second electromagnetic winding.

In one embodiment, a second outer pole is provided to define, together with the lower core region, the second volume for receiving the second electromagnetic winding.

Alternatively, the first outer pole may be of an extended length to receive both the upper core region and the lower core region. In other words, the first outer pole surrounds both the first and second windings. In this embodiment the actuator arrangement is a twin, double pole actuator arrangement with the first outer pole defining the outer pole of both actuators and the inner core defining the other pole of both actuators.

In a further alternative, the first outer pole is formed in two parts, a first part defining the first volume and a second part defining the second volume.

According to a third aspect of the invention, there is provided a fuel injector for use in an internal combustion engine, including a valve needle which is operable by means of a valve arrangement to control injection by the injector, and an actuator arrangement for controlling the valve arrangement, wherein the actuator arrangement is of the type set out in the first or second aspect of the invention.

It will be appreciated that preferred and/or optional features of the actuator arrangement of the first aspect of the invention may be incorporated within the actuator arrangement of the second aspect of the invention and the fuel injector of the third aspect of the invention also.

In one example, the valve arrangement includes a spill valve for controlling fuel pressure within an injector supply passage.

In another example, the valve arrangement includes a nozzle control valve for controlling fuel pressure in an injector control chamber.

In a still further example, the valve arrangement includes a spill valve for controlling fuel pressure within an injector supply passage and a nozzle control valve for controlling fuel pressure in an injector control chamber so as to control movement of the valve needle. Energisation and/or de-energisation of the first electromagnetic winding controls the spill valve, and the injector further comprises a second electromagnetic winding, wound on the lower core region of the actuator arrangement, whereby energisation and/or de-energisation of the second electromagnetic winding controls the nozzle control valve.

In this case the injector may further include a second outer pole which defines, together with the lower core region, a second volume for receiving the second electromagnetic winding.

In another case, the first outer pole has an extended length to receive both the upper core region and the lower core region so that the first outer pole, together with the lower core region, defines a second volume for receiving a second electromagnetic winding, as mentioned previously.

Alternatively, the first outer pole is formed in two parts, a first part defining the first volume and a second part defining a second volume for receiving a second electromagnetic winding.

In any aspect of the invention, at least one of the laminates of the inner core may have an outer profile that is different to that of its neighbouring laminate.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a sectional view through a known fuel injector within which an actuator arrangement of the present invention may be used,

FIG. 2 is an enlarged sectional view of an actuator arrangement in another known fuel injector;

FIG. 3 is a perspective view of the actuator arrangement of a first embodiment of the invention, but with the windings of the actuator arrangement removed;

FIG. 4 is a cut-away view of the actuator arrangement shown in FIG. 3, with the windings in place;

FIG. 5 is a perspective view of the actuator arrangement in FIGS. 3 and 4, also illustrating an electrical connector to the winding;

FIG. 6 is a perspective view of the actuator arrangement in FIGS. 3 and 4, when housed within an actuator housing;

FIG. 7 is a perspective view of the inner core of the actuator arrangement in FIGS. 3 to 6, showing upper and lower laminated core regions and a laminated collar,

FIG. 8 is a perspective view of the inner core in FIG. 7, with a part of the laminated collar removed;

FIG. 9 is a perspective view of four different laminates forming part of the laminated core regions in FIGS. 7 and 8;

FIG. 10 is a perspective view of the laminated collar of the actuator arrangement in FIGS. 7 and 8; and

FIGS. 11 and 12 are top plan views of the actuator arrangement in FIGS. 4 to 10 to illustrate the effect of variation in nominal laminate layer thickness for the laminated core regions.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following description relates to an actuator arrangement, or actuator assembly, of the type suitable for use in the injector illustrated in FIG. 1, or the injector illustrated in FIG. 2, in which a spill valve 14 controls fuel pressure within an injector delivery chamber 17 and a nozzle control valve 12 controls injection by moving an injector valve needle 16.

Referring to FIGS. 3 to 5, the actuator assembly defines an actuator axis A and includes a laminated core structure (referred to generally as 40), in the form of an inner pole or core, and a first outer pole (referred to generally as 42). As can be seen most clearly in FIG. 4, the inner core 40 has three distinct regions; an upper core region 44 having a first diameter, D1, a lower core region 46 having a second diameter, D2, and a collar 48 having a third diameter D3 which projects circumferentially from the base of the upper core region 44, where it meets the lower core region 46. The first and second diameters D1, D2 of the upper and lower core regions 44, 46 are similar, but with the second diameter D2 fractionally less than the first diameter D1. The diameter D3 of the collar 48 is greater than the diameters D1 and D2 so as to define a platform upon which the outer pole 42 is supported or rests.

The outer pole 42 is of generally annular form and defines an internal bore 50 within which the upper core region 44 is received, the internal bore 50 of the outer pole 42 and the outer surface of the upper core region 44 together defining a first volume for receiving a first winding or solenoid 52 of the actuator assembly (only shown in FIGS. 4 and 5). The first winding 52 is wound onto the upper core region 44 by means of a winding bobbin (not shown) in a manner which would be familiar to a person skilled in the art.

Referring specifically to FIG. 4, the actuator assembly further includes an electrical connector 54 to permit a current to be applied to the winding 52, in use, so as to energise the winding. For this purpose, the outer pole 42 is also provided with an opening 56 to permit connecting wires (not identified) to pass between the electrical connector 54 and the winding 52.

The upper region 44 of the inner core 40 forms one of the poles of a double pole actuator for the spill valve of the fuel injector. The double pole actuator generates a magnetic field upon application of the electric current to the winding 52, so that the resultant magnetic field drives movement of an armature (not shown) located above (in the orientation shown) the inner core 40. The lower region 46 of the inner core 40 provides the single pole of an actuator for the nozzle control valve of the injector. A second winding 59 (shown only in FIGS. 4 and 5) for the inner core 40 is wound around the lower core region 46, with suitable electrical connections being made to the second winding 59 via the electrical connector 54.

As illustrated in FIG. 6, the entire actuator assembly locates within an external housing part 57, which typically forms a part of the injector housing (such as that shown in FIG. 1 or FIG. 2).

It is a particular feature of the invention that the upper and lower regions 44, 46 of the inner core 40 are laminated, and so too is the collar 48. Referring to FIGS. 7 to 9, the upper and lower regions 44, 46 comprise a plurality of distinct laminate layers or ‘laminates’, two of which are identified at 140, with each laminate being of different shape to its neighbouring laminate or laminates. The laminates 140 are stacked along (i.e. in the direction of) a lamination axis L_(A) which is perpendicular to the actuator axis A. Thus, in the orientation shown, the laminates 140 are arranged in a vertical fashion, one next to the other.

As can be seen most clearly in FIGS. 8 and 9, due to the difference in diameter between the upper and lower core regions 44, 46, outermost ones of the laminate (for example—140 a in FIG. 9) will be generally T-shaped, having a stem 142 which terminates in a cross member 144, whereas internal ones of the laminates (for example—140 b in FIG. 9) will be generally cross-shaped so that the stem projects on both sides of the cross member 144. The cross member 144 of each laminate 140 is provided with a recess 146 at each of its outermost ends. When the laminates 140 are stacked next to one another, the recesses 146 together define a channel 148 which cooperates with the outer collar 48 of the inner core 40, as discussed further below, so as to lock the parts together. The laminates 140 are stamped from sheet laminate using conventional tooling so that each has the same nominal thickness. Referring to FIG. 7 specifically, by way of example it is envisaged that each of the laminates 140 forming the upper and lower core regions 44, 46 has a thickness, to, of approximately 0.3 to 0.5 millimetres. For an actuator having a 20 mm core diameter, for example, this would result in between 40 and 60 individual laminates 140 making up the inner core 40. Typically, the width, w, of the laminate stem 142 on the upper core region 44 will be between 4 and 13.5 millimetres. Preferably, the laminates 140 may be formed from silicon iron (SiFe).

Referring to FIG. 10, the collar 48 includes a plurality of laminate layers, or ‘laminates’, two of which are identified at 240. The laminates 240 of the outer collar 48 are stacked along a lamination axis, L_(B), which is perpendicular to the lamination axis, L_(A), of the upper and lower core regions 44, 66. In other words, whereas the laminates 140 of the upper and lower core regions 44, 46 are stacked vertically, the laminates 240 of the collar 48 are stacked horizontally.

The laminates 240 of the outer collar 48 together define an internal collar periphery 242 of generally square form which is cooperably shaped to mate with the outer profiles of the laminates 140 of the upper and lower core regions 44, 46. The outer periphery of the collar 48 is of generally circular form so as to match the internal bore 50 of the first pole 42. The collar 48 defines a primary cross axis C_(A) and a secondary cross axis C_(B) (both identified in FIG. 10), with the axes C_(A), C_(B), being perpendicular to one another.

The laminated collar 48 is formed in two halves to define two outer collar parts 48 a, 48 b, each of which comprises five horizontally stacked laminates. For the purpose of the following description, the laminates of the collar will be numbered as laminates 1, 2, 3, 4 and 5, working from the upper surface of the collar 48 to the lower surface. Each of the laminates 1, 2, 3, 4, 5 is shaped so as to define a part circular outer periphery, an internal opening and first and second end regions (e.g. 1 a, 1 b for laminate 1). The first and second end regions 1 a, 1 b of the laminates of one collar part 48 a face and mate with the first and second end regions 1 a, 1 b, respectively, of the other collar part 48 b.

Laminate 3 on each part 48 a, 48 b of the collar 48 defines a square shaped internal opening 242 a which is of narrower width (along the primary cross axis C_(A)) compared to the other laminates 1, 2, 4 and 5 by virtue of a projection defined by a region of enlarged width 244 of each end region 1 a, 1 b. The region of enlarged width 244 is provided so as to be received within the core channel 148 (as shown in FIG. 8), thus serving to lock the various core parts 44, 46 and 48 together.

The end regions 1 a, 1 b of alternate ones of the laminates 1 to 5 are dimensioned so that, on one collar part 48 b, the end regions 1 a, 1 b of laminates 1, 3 and 5 are longer, along the secondary cross axis C_(B), than the end regions 1 a, 1 b of laminates 2 and 4 of the same collar part 48 b and, on the other collar part 48 a laminates 1, 3 and 5 are shorter, along the secondary cross axis C_(B), than the end regions 1 a, 1 b of laminates 2 and 4 of the same collar part 48 a. The end regions 1 a, 1 b of the laminates 1 to 5 therefore define a means for interlocking or engaging the outer collar parts 48 a, 48 b together in such a manner that the degree of overlap between the laminate end regions 1 a, 1 b may be varied along the secondary cross axis L_(B), whereas movement perpendicular to the cross axes (i.e. along the actuator axis A) is prevented.

By way of further explanation, if, for example, the laminates 1 to 5 of each outer collar part 48, 48 b are fully engaged, the diameter of the outer collar 48 along the secondary cross axis C_(B) will be smaller than the diameter of the outer collar 48 if the laminates 1 to 5 are only partially engaged. In FIGS. 7 and 10, for example, the laminates 1 to 5 are shown as being partially engaged only, leaving a small degree of separation between the facing end regions 1 a, 1 b of the respective parts 48 a, 48 b. It will be appreciated that regardless of the degree of overlap between the end regions 1 a, 1 b of the collar parts 48 a, 48 b, the diameter of the collar 48 along the primary cross axis C_(A) remains unchanged.

It is a particular benefit of the present invention that the variable degree of engagement between the collar parts 48 a, 48 b provides a means for compensating for differences in the nominal thickness of the laminates 140 of the upper and lower core regions 44, 46. This is best illustrated with reference to FIGS. 11 and 12, which show top plan views of the inner core 40 of the actuator (parts 44 and 48 are visible) where the thickness of the laminates 140 in each Figure is different.

In FIG. 11, the thickness of the laminates is equal to a nominal value, t1, which results in the outer periphery of the upper core region 44 being of circular form. If, however, the thickness of each laminate 140 is less than the nominal thickness, t1, then when the laminate layers 140 are assembled together the outer periphery of the upper core region 44 will be of oval or elliptical form, rather than circular. This is undesirable for a number of reasons. For example, the winding bobbin used to wind the solenoid winding 52 onto the inner core 40 is designed specifically to wind onto a circular core, not an elliptical one, and so manufacturing problems arise if the inner core 40 has a degree of ellipticity. For this reason the tool for stamping the laminates 140 automatically adjusts the width, w1, of the laminate stem 142 in response to the measured laminate thickness to ensure a circular outer diameter is always achieved for the upper core region 44, regardless of thickness variations.

Referring to FIG. 12, here the thickness, t2, of the laminates 140 is less than the nominal thickness t1, as shown in FIG. 11, but the widths, w2, of the laminate stems are increased (compared to widths, w1, in FIG. 11) so that the outer periphery of the upper core region 44 maintains a circular form, albeit with slightly ‘flatter’ edges due to the increased stem width w2. Although the diameter of the upper core region 44 is slightly reduced, this does not matter providing the outer diameter maintains a circular form.

The facility to be able to adjust the outer diameter of the upper and lower core regions 44, 46 so as to maintain the outer circular profile addresses the problem encountered previously whereby either the circular outer profile of the upper core region 44 has an undesirable degree of ellipticity or the diameter is reduced so that the upper core region 44 is no longer compatible with the remainder of the assembly and/or the assembly tools.

By virtue of the adjustable collar 48 of the present invention, variations in the diameter of the upper core region 44 in nominally identical parts allow a single collar part 48 to be manufactured to fit with any laminated inner core structure 40, regardless of laminate thickness.

It is one consequence of adjusting the laminate widths in the upper core region 44 to maintain a circular outer periphery for the upper core region 44 that the outer periphery of the lower core region 46 will become elliptical. This is because the machine tool that adjusts the laminate width does so for both the region of the stem at the upper region 44 and the region of the stem at the lower region. This represents a compromise to the ideal of having two exactly circular core regions 44, 46, but nonetheless provides an improvement.

Although it is beneficial for the inner core 40 of the actuator to be laminated as described previously, it is preferable for the outer pole 42 to be a unitary and rigid structure. This is because, magnetically, the inner core 40 tends to have less material to conduct magnetic flux, and so tends to reach saturation before other regions. Thus, the use of magnetically ‘good’, grain oriented material, such as that typically used for laminates, is advantageous. Conversely, the first outer pole 42 is of relatively large circumference, and hence comprises a large amount of material, and so does not tend to saturate so readily. For this reason there is no requirement for the first outer pole 42 to be laminated. Furthermore, the ring-like outer pole 42 proves greater structural integrity, so that the co-operable surfaces of the inner core and the outer pole mate together well. Magnetic performance is also improved.

In order to assemble the actuator, the following sequence of steps may be applied. Firstly, the laminated inner core 40 is assembled using the laminating procedures discussed previously. Secondly, the first winding 52 is wound upon the upper region 44 of the inner core 40 by means of the winding bobbin so as to occupy the winding volume and the second winding 59 is wound around the lower region 46 of the inner core 40. The first outer pole 42 is received over the top of the upper region 44 so that the lower surface of the outer pole mates with the upper surface of the laminates 240 (i.e. laminates 1) of the collar parts 48 a, 48 b. Finally, the entire assembly is received into the actuator housing 57 (as shown in FIG. 6) ready for assembly with the remaining injector parts.

In another embodiment of the invention (not shown), a twin, double pole actuator arrangement includes a second, outer pole to encompass the lower region 46 of the inner core 40 and the second winding 59 (i.e. each of the upper and lower core regions forms a part of a double pole arrangement). FIG. 1 illustrates an injector for use with a twin-double pole actuator arrangement of this alternative embodiment. In this arrangement, the windings 24, 26 would be wound in the same direction, with the laminated collar 48 of the actuator's inner core 40 defining a part of the flux path for both windings so that only a relatively small net flux flows through the collar 48.

In a twin double pole actuator arrangement of the above mentioned type, the first outer pole 42 may itself define both the first volume for the first winding 52 and the second volume for the second winding 59 (as best seen in FIG. 4). The first outer pole 42 may be of extended length so as to extend below the collar 48 to surround the lower core region 46 or, alternatively, may be formed from two separate parts, one part defining the first volume and one part defining the second volume.

It will be appreciated that although the injectors have been described as those in which a spill valve is included, this need not be the case and equally the invention is applicable to a common rail injector in which only a nozzle control valve is provided to control the valve needle. Equally, the invention is applicable to an injector in which only a spill valve is provided, but without a nozzle control valve, in which case there is no requirement for a second winding on the lower core region 46, and, (optionally), no requirement for the lower core region 46.

Although in the aforementioned embodiment it is envisaged that all the laminates of the inner core have a different form to their neighbouring laminate layer, inner core profiles are envisaged in which some laminates are of the same shape, depending upon the thickness of the laminate layers.

Having described the particularly preferred embodiments of the present invention, it is to be appreciated that these embodiments are exemplary only and that variations and modifications such as will occur to those possessed of the appropriate knowledge and skills may be made without departure from the scope of the invention as set forth previously. 

1. An actuator arrangement for use in a fuel injector of an internal combustion engine, the actuator arrangement including: an inner core (40) comprising a collar (48) and a core region (44) having a plurality of laminates (140) stacked in the direction of a first lamination axis (L_(A)), a first outer pole (42) for receiving at least a part of the core region (44), and an electromagnetic winding (52) for receipt within a first volume defined between the first outer pole (42) and the core region (44), wherein the collar (48) is formed from at least two collar parts (48 a, 48 b) which are adjustable relative to one another to alter the separation between them so as to accommodate core regions (44) of different diameter.
 2. The actuator arrangement as claimed in claim 1, wherein the collar (48) is formed from a plurality of laminates (1, 2, 3, 4, 5) having a second lamination axis (A) which is perpendicular to the first lamination axis (L_(A)).
 3. The actuator arrangement as claimed in claim 2, wherein the plurality of laminates (1, 2, 3, 4, 5) of the collar (48) define an internal periphery (242) which mates with an outer periphery defined by the laminates (140) of the core region (44).
 4. The actuator arrangement as claimed in claim 3, wherein the internal periphery (242) of the collar (48) and the plurality of laminates (140) of the core region (44) include an interlocking arrangement (148, 244) for locking the outer collar (48) and the core region (44) together so as to prevent relative movement along the second lamination axis (A).
 5. The actuator arrangement as claimed in claim 4, wherein the interlocking arrangement includes a channel (148) defined by one or more of the plurality of laminates (140) of the core region (44), and a projection (244) provided on one or more of the plurality of laminates of the collar (48), wherein the projection (244) is received within the channel (148).
 6. The actuator arrangement as claimed in claim 1, wherein the inner core (40) comprises an upper core region (44) which defines, together with the first outer pole (42), the first winding volume for the first electromagnetic winding (52).
 7. The actuator arrangement as claimed in claim 6, wherein the inner core (40) further comprises a lower core region (46) which defines, at least in part, a second volume for receiving a second electromagnetic winding.
 8. The actuator arrangement as claimed in claim 7, further comprising a second outer pole which defines, together with the lower core region (46), the second volume for receiving the second electromagnetic winding.
 9. The actuator arrangement as claimed in claim 7, wherein the first outer pole (42) has an extended length so as to surround both the upper core region (44) and the lower core region (46), wherein the first outer pole (42) defines, together with the lower core region (46), the second volume for receiving the second electromagnetic winding.
 10. The actuator arrangement as claimed in claim 7, wherein the first outer pole (42) is formed in two parts, a first part defining the first volume and a second part defining the second volume.
 11. The actuator arrangement as claimed in claim 1, wherein at least one of the laminates (140) of the inner core (40) is different in outer profile to its neighbouring laminate or laminates.
 12. The actuator arrangement as claimed in claim 1, wherein the actuator arrangement has an actuator axis (A) and wherein the first lamination axis (L_(A)) is substantially perpendicular to the actuator axis (A).
 13. An actuator arrangement for use in a fuel injector of an internal combustion engine, the actuator arrangement including: an inner core (40) comprising a collar (48) and a core region (44) having a plurality of laminates (140) stacked in the direction of a first lamination axis (L_(A)), a first outer pole (42) for receiving at least a part of the core region (44), and an electromagnetic winding (52) for receipt within a first volume defined between the first outer pole (42) and the core region (44), wherein the collar (48) is formed from a plurality of laminates (1, 2, 3, 4, 5) stacked in the direction of a second lamination axis (A) which is perpendicular to the first lamination axis (L_(A))
 14. The actuator arrangement as claimed in claim 13, wherein the inner core (40) comprises an upper core region (44) which defines, together with the first outer pole (42), the first winding volume for the first electromagnetic winding (52).
 15. The actuator arrangement as claimed in claim 13, wherein the inner core (40) further comprises a lower core region (46) which defines, at least in part, a second volume for receiving a second electromagnetic winding.
 16. The actuator arrangement as claimed in claim 15, further comprising a second outer pole which defines, together with the lower core region (46), the second volume for receiving the second electromagnetic winding.
 17. A fuel injector for use in an internal combustion engine, the fuel injector including: a valve needle (16) which is operable by means of a valve arrangement so as to control injection by the injector, and an actuator arrangement for controlling the valve arrangement, wherein the actuator arrangement includes an inner core (40) comprising a collar (48) and a core region (44) having a plurality of laminates (140) stacked in the direction of a first lamination axis (L_(A)), a first outer pole (42) for receiving at least a part of the core region (44), and an electromagnetic winding (52) for receipt within a first volume defined between the first outer pole (42) and the core region (44), wherein the collar (48) is formed from at least two collar parts (48 a, 48 b) which are adjustable relative to one another to alter the separation between them, thereby to accommodate core regions (44) of different diameter.
 18. The injector as claimed in claim 17, wherein the collar (48) is carried part-way along the axis of the inner core (40) with an upper core region (44) on one side of the collar (48) and a lower core region (46) on the other side of the collar (48).
 19. The injector as claimed in claim 17, wherein the upper core region (44) defines, together with the first outer pole (42), the first volume for receiving the first electromagnetic winding (52).
 20. The injector as claimed in claim 19, wherein the valve arrangement includes a spill valve (14) for controlling fuel pressure within an injector supply passage (20).
 21. The injector as claimed in claim 19, wherein the valve arrangement includes a nozzle control valve (12) for controlling fuel pressure in an injector control chamber (22).
 22. The injector as claimed in claim 19, wherein the valve arrangement includes a spill valve (14) for controlling fuel pressure within an injector supply passage (20) and a nozzle control valve (12) for controlling fuel pressure in an injector control chamber (22) so as to control movement of the valve needle (16), whereby energisation and/or de-energisation of the first electromagnetic winding (52) controls the spill valve (14), the injector further comprising a second electromagnetic winding, wound on the lower core region (46), whereby energisation and/or de-energisation of the second electromagnetic winding (59) controls the nozzle control valve (12).
 23. The injector as claimed in claim 22, further comprising a second outer pole which defines, together with the lower core region (46), a second volume for receiving the second electromagnetic winding (59).
 24. The injector as claimed in claim 23, wherein the first outer pole (42) has an extended length so as to surround both the upper core region (44) and the lower core region (46) and wherein the first outer pole (42) defines, together with the lower core region (46), a second volume for receiving a second electromagnetic winding (59).
 25. The injector as claimed in claim 23, wherein the first outer pole (42) is formed in two parts, a first part defining the first volume and a second part defining a second volume for receiving a second electromagnetic winding (59).
 26. The injector as claimed in claim 17, wherein at least one of the laminates (140) of the inner core (40) has an outer profile that is different to that of its neighbouring laminate.
 27. A fuel injector for use in an internal combustion engine, the fuel injector including: a valve needle (16) which is operable by means of a valve arrangement so as to control injection by the injector, and an actuator arrangement for controlling the valve arrangement, wherein the actuator arrangement includes an inner core (40) comprising a collar (48) and a core region (44) having a plurality of laminates (140) stacked in the direction of a first lamination axis (L_(A)), a first outer pole (42) for receiving at least a part of the core region (44), and an electromagnetic winding (52) for receipt within a first volume defined between the first outer pole (42) and the core region (44), wherein the collar (48) is formed from a plurality of laminates (1, 2, 3, 4, 5) stacked in the direction of a second lamination axis (A) which is perpendicular to the first lamination axis (L_(A)). 